Skype, the online telephone service that eBay Inc. bought for $2.6 billion two years ago, has failed to live up to expectations, leading the San Jose auction service to take a $900 million charge, company officials said Monday, essentially acknowledging that they overpaid for the property.

In addition, eBay said that Niklas Zennstrom, Skype's chief executive and co-founder, has resigned.

EBay, in San Jose, acquired Skype in 2005 so that buyers and sellers on its popular online shopping site could easily call one another, under the theory that providing a more personal touch would elicit more sales. Executives also talked about Skype promoting eBay's online payment division, PayPal, and serving as the backbone for online ads that rely on Internet telephone calls rather than eyeballs.

But critics quickly questioned the wisdom of combining such different companies, not to mention the acquisition's price tag. Although highly popular, Skype barely had any revenue when bought because it was largely a free service.

Calls on Skype from one computer to another computer are free. Only people who use the service to call from a computer to a telephone pay per-minute fees.

After defending the acquisition for some time, Meg Whitman, eBay's chief executive, acknowledged recently that Skype has failed to make as much of a splash as hoped. During a conference call three months ago, she said: "Skype has delivered in many of these areas, but it is not where we want it to be in terms of user activity. This will require increased attention and focus from the leadership team."

As part of the company's announcement Monday, eBay said it would take a charge of approximately $900 million in the third quarter for Skype, accounting for the service being worth less today than when acquired.

EBay also agreed to take another charge of $530 million to settle future payments to Skype's original shareholders for the unit meeting certain performance goals through the first half of 2009 as called for in the acquisition contract. However, the unit apparently is failing to meet some of the loftiest goals because the pay out could have been as much as $1.7 billion.

Hani Durzy, an eBay spokesman, said that Zennstrom could have stayed with Skype, and that his departure was voluntary. He will become chairman of the subsidiary.

In addition to co-founding Skype, Zennstrom founded the KaZaA file sharing service and is currently working on Joost, which helps distribute television shows online. Michael van Swaaij, eBay's chief strategy officer, will serve as Skype's chief executive until a replacement is found.

Also resigning his post was Henry Gomez, who served as Skype's president. He will focus on his other role at eBay as a senior vice president. Gomez was Skype's third president in two years.

Patrick Monaghan, an analyst with Yankee Group, called eBay's Skype acquisition a mistake and said: "There never seemed to be a clear business strategy about how the companies would interact. If you're selling something on eBay, you can click to call someone who is selling an item, but ... there isn't much else behind it."

Because the cost of Internet calls is declining, he said, Skype will have an increasingly difficult time earning much money from its core business. EBay, he added, may in the end spin off the unit as a separate company.

Skype's revenue, though growing quickly, was tiny by Internet giant standards at $90 million in the second quarter, up from $44 million a year earlier. The contribution barely makes a dent in eBay's overall business, which had $1.83 billion in revenue in the second quarter.

Skype had 220 million registered user accounts in June, although it's unclear how many of those accounts were active. The service's users spent 7.1 billion minutes on free calls during that period, flat from the same period a year earlier. The number of paid minutes was 1.3 billion, a 57 percent increase from the previous year.

"We're disappointed that Skype still hasn't performed as well in the short term as we had hoped, but we still belive in Skype" in the long term, Durzy said.